Question

The constant power output of a machine is 6 W. The energy delivered by it in 2 minutes is:

Options

A
12 joules
B
720 joules
C
72 joules
D
3 joules
E
120 joules

Explanation

This is incorrect because it results from a wrong calculation or misunderstanding of units. The machine operates for 120 seconds, not 2 seconds or 0.2 minutes. Using the correct formula gives 720 J, not 12 J.

This is the correct answer.

Power is the rate of doing work or transferring energy per second

This means the machine delivers 720 joules of energy in 2 minutes..

This is incorrect. It appears to be an error due to missing one zero (perhaps using 12 s instead of 120 s). Always convert minutes to seconds before substituting into the formula.

This option is incorrect and far too small. It would correspond to an extremely short operation time (less than a second). A 6 W machine working for 2 minutes can never deliver only 3 J of energy.

Also incorrect. This might come from using 20 s instead of 120 s. But since 2 minutes equals 120 s, the energy must be much greater. The correct answer remains 720 J.